Rookie here may rebuild a 250 cid--need advice

[Anonymous]

Own a '62 Comet who's 170 cid is toast (blue smoke, major compression loss). Picked up a '74 250 cid from a Mav. to replace the 170. Sadly, 2 of my other cars blew out their trannies this spring, so I'm down about $3k. I was thinking the 250 should get rebuilt. I've never done this. I was told the 250 did not smoke when it last ran, several months ago. Should I do a total rebuild (pistons, cam, etc. with machine milling of block) while it sits on the engine stand or just a basic (flush, gaskets, & small hardware). My finances are low, but the car does not need to be running soon. I already have the Ford Six Per. Handbk, but feel I need more info and advice before proceeding. Also on the hunt for a shade tree mechanic in Cols. OH who can drink my beer and belch while I do most of the labor, just giving handy advice when appropriate so I don't smash my forehead against the cinder blocks TOO much while attempting this project. Thnx

 

[61Futura]

Before you go rebuilding the engine, first see if you can install it. You will need a new radiator, motor mounts, air cleaner, V8 style tranny with yoke, starter?, driveshaft, a '65 V8 steering center link, and still have a fan issue. And how tough is the Comets rear end? See if you can trade the 250 in on a 200 or 170. The money you save in beer alone, should pay for 5 tanks of gasoline.

Steve

 

[CZLN6]

Howdy Creesto:

Welcome to the Forum.

The choice is yours on the build/no build question, But....

The 250 is relatively simple to work on. Be sure to get and study a shop manual that includes the 250 in the engine section. The 250 is very similiar to the 200, with a few specific exceptions.

The largest engineering hurdle in getting performance and economy out of a 250 is the huge deck clearance. Most 250 came with somewhere between .100" and .150" deck height alone. Add the thickness of the head gasket and you get "TOO MUCH"!

The least expensive way to deal with this problem is to use 255 V8 pistons which stand .085" taller and deck the top of the block to zero. Next you will need to control compression. That can be done by spending some time unshrouding the chambers and/or milling a "D" shaped dish into the top of the V8 pistons that mirrors the shape of the combustion chambers. The "D" shaped dish has several advantages; it lightens the pistons, maintains a high quench to bore ratio, and gains the combustion efficiency of a dished piston.

The other option is to use the rods from a Tempo HSC 2.3 4 cylinder. IIRC they stand .125" taller than 250 rods and are compatible with 250 pistons. To the best of my knowledge this is an untried solution, but it is on my list. The longer rods increase the rod length to stroke ratio slightly. Piston choices in this case could be large dish 200/250 pistons, small dish, flat top HSC- each offering higher compression.

Even at zero deck height, the head gaskets available now-a-days will give you more than enough deck clearance.

Also be sure to specify cam gears for a '72 and earlier 250 to be sure to get straight up cam timing.

Adios, David

 

[xctasy]

Howdy Creesto:.....

The other option is to use the rods from a Tempo HSC 2.3 4 cylinder. IIRC they stand .125" taller than 250 rods and are compatible with 250 pistons. To the best of my knowledge this is an untried solution, but it is on my list. The longer rods increase the rod length to stroke ratio slightly. Piston choices in this case could be large dish 200/250 pistons, small dish, flat top HSC- each offering higher compression.

Adios, David

Just a quick note. 2.3 HSC rods are 5.45", and the only thing they fit are a few 188 or 221 Argie engines. The ones to use are the Taurus and Tempo 2.5 HSC. Rather rare, they are found on 86 to 95 Taurus/Tempo models, and are 6.00" tall and should fit easily in theory. Our Aussie 4.0 AU rods are almost the same, at 6.06". Same wrist 0.912" pin, same size 2.124" rod bearing.

The 250's deck issue should be able to be sorted if you can get a supply of 2.5 HSC or 4.0 AU or BA rods for a sensible price.

 

[DaGr8Tim]

Just a quick note. 2.3 HSC rods are 5.45", and the only thing they fit are a few 188 or 221 Argie engines. The ones to use are the Taurus and Tempo 2.5 HSC. Rather rare, they are found on 86 to 95 Taurus/Tempo models, and are 6.00" tall and should fit easily in theory. Our Aussie 4.0 AU rods are almost the same, at 6.06". Same wrist 0.912" pin, same size 2.124" rod bearing.

The 250's deck issue should be able to be sorted if you can get a supply of 2.5 HSC or 4.0 AU or BA rods for a sensible price.

Not to bust your bubble, even partially. But the 2.5 HSC was only used in the Ford Taurus from 86-91. It was the base engine, but even then most were produced with a the 3.0 v6.

 

[Anonymous]

So instead of just doing a simple rebuild of the 250, I hear you guys saying I should also retool it with different pistons, rods etc. OH BTW< it has a C4 tranny already attached. Why do I need to upgrade my steering to a Vee8 drag link-linkage issues?

OK, I can see decking the block to help with the known clearance issues. The FordSix PerfHandbk addresses the other 'fit' issues pretty clearly, from the motor mounts (which came out of the '74Mav w/ the engine) to the radiator placement and elecfan.

Since I have plenty of time on this, does it make sense to tackle the rebuild one 'end' at at time? Do the bottom end first, then rework the top end, etc.? With decking and reboring, how much can I expect to spend on the machine shop work? And how much more for the D shaping on the piston tops?

I'm getting excited about this, but I'm also a bit intimidated. Can anyone tell me of a decent rebuild manual for an early '70s 250cid Ford I6? I've goggled around and not found much.

 

[61Futura]

The starter is mounted lower on the bellhousing of a 250 and it will require a lower center link to to clear it. Or so I have been told. I believe the yoke on the back of the tranny won't hook up to your driveshaft, so a larger end has to be welded onto the front of your current driveshaft.

Maybe a 62 Comet has different parts under it than my 61 Falcon and I'm wrong about how many things have to change for you. You've probably got heavier front suspension, but that is little help for this. It sure would be a nice gain of torque & horsepower to shoehorn a 250 under the hood.

Steve